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Background and Objective Although Cynanchum wilfordii Hemsley (C. wilfordii) has been widely used for treating insomnia in Korea, there are no objective data on its sleep-enhancing effects. Methods We examined the effects of this extract on sleep latency, sleep parameters, and NREM delta activity in rats administered several different dosages (300 mg/kg, 1 g/kg or 3 g/kg, p.o.) and compared them to valerian extract which is a popular natural hypnotic. Results We found no significant shortening of sleep latency was observed with any dosage of either C. wilfordii extract or with valerian. NREM sleep increased significantly at C. wilfordii dosages of 300 mg/kg and 1 g/kg but not for 3 g/kg. Only the 1 g/kg dosage significantly decreased the amount of wakefulness. Neither any of the C. wilfordii dosages nor valerian extract produced any effect on REM sleep amount. Conclusions Therefore, C. wilfordii could be a useful natural hypnotic with a sleep-enhancing effect.